Cooling system

ABSTRACT

An apparatus includes an expansion valve, a load, a sensor, an exhaust system, and a controller. The expansion valve cools a refrigerant. The load uses the refrigerant to cool a space. The sensor detects a concentration of the refrigerant in the space. The exhaust system evacuates the refrigerant from the space. The controller determines whether the detected concentration of the refrigerant in the space exceeds a first threshold and in response to a determination that the detected concentration of the refrigerant exceeds the first threshold, closes the expansion valve. The controller also determines whether the detected concentration of the refrigerant in the space exceeds a second threshold and in response to a determination that the detected concentration of the refrigerant exceeds the second threshold, activates the exhaust system.

TECHNICAL FIELD

This disclosure relates generally to a cooling system, such as arefrigeration system.

BACKGROUND

Cooling systems are used to cool spaces, such as residential dwellings,commercial buildings, and/or refrigeration units. These systems cycle arefrigerant (also referred to as charge) that is used to cool thespaces.

SUMMARY OF THE DISCLOSURE

This disclosure contemplates an unconventional cooling system thatdetects and responds to refrigerant leaks based on the detectedconcentrations of leaked refrigerant. The system includes a sensor thatdetects a concentration of leaked refrigerant in a space cooled by aload. When that detected concentration exceeds a first threshold, thesystem closes an expansion valve supplying refrigerant to a load to stopthe flow of refrigerant to that load. If the leak continues and thedetected concentration exceeds a second threshold, the system activatesan exhaust system designed to evacuate the leaked refrigerant from thespace. Certain embodiments will be described below.

According to an embodiment, an apparatus includes an expansion valve, aload, a sensor, an exhaust system, and a controller. The expansion valvecools a refrigerant. The load uses the refrigerant to cool a space. Thesensor detects a concentration of the refrigerant in the space. Theexhaust system evacuates the refrigerant from the space. The controllerdetermines whether the detected concentration of the refrigerant in thespace exceeds a first threshold and in response to a determination thatthe detected concentration of the refrigerant exceeds the firstthreshold, closes the expansion valve. The controller also determineswhether the detected concentration of the refrigerant in the spaceexceeds a second threshold and in response to a determination that thedetected concentration of the refrigerant exceeds the second threshold,activates the exhaust system.

According to another embodiment, a method includes cooling a refrigerantusing an expansion valve and using the refrigerant to cool a spaceproximate a load. The method also includes detecting a concentration ofthe refrigerant in the space using a sensor. The method further includesdetermining whether the detected concentration of the refrigerant in thespace exceeds a first threshold and in response to a determination thatthe detected concentration of the refrigerant exceeds the firstthreshold, closing the expansion valve. The method also includesdetermining whether the detected concentration of the refrigerant in thespace exceeds a second threshold and in response to a determination thatthe detected concentration of the refrigerant exceeds the secondthreshold, activating an exhaust system to evacuate the refrigerant fromthe space.

According to yet another embodiment, a system includes a high side heatexchanger, an expansion valve, a load, a sensor, an exhaust system, anda controller. The high side heat exchanger removes heat from arefrigerant. The expansion valve cools the refrigerant from the highside heat exchanger. The load uses the refrigerant to cool a space. Thesensor detects a concentration of the refrigerant in the space. Theexhaust system evacuates the refrigerant from the space. The controllerdetermines whether the detected concentration of the refrigerant in thespace exceeds a first threshold and in response to a determination thatthe detected concentration of the refrigerant exceeds the firstthreshold, closes the expansion valve. The controller also determineswhether the detected concentration of the refrigerant in the spaceexceeds a second threshold and in response to a determination that thedetected concentration of the refrigerant exceeds the second threshold,activates the exhaust system.

Certain embodiments provide one or more technical advantages. Forexample, an embodiment detects and isolates refrigerant leaks by closingan expansion valve when a detected refrigerant concentration in a spaceexceeds a first threshold. As another example, an embodiment maintainsthe safety of a space by activating an exhaust system to evacuate leakedrefrigerant from the space when the detected concentration of the leakedrefrigerant exceeds a second threshold. In some embodiments, leaks inthe cooling system are isolated when they occur, which may prevent theentire cooling system from being shut down to diagnose and repair theleak. Certain embodiments may include none, some, or all of the abovetechnical advantages. One or more other technical advantages may bereadily apparent to one skilled in the art from the figures,descriptions, and claims included herein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, referenceis now made to the following description, taken in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates portions of an example cooling system;

FIG. 2 illustrates portions of the cooling system of FIG. 1; and

FIG. 3 is a flowchart illustrating a method for operating the coolingsystem of FIG. 1.

DETAILED DESCRIPTION

Embodiments of the present disclosure and its advantages are bestunderstood by referring to FIGS. 1 through 3 of the drawings, likenumerals being used for like and corresponding parts of the variousdrawings.

Cooling systems are used to cool spaces such as residential dwellings,commercial buildings and/or refrigeration units. These systems cycle arefrigerant that is used to cool the spaces. In a retail setting, thecooling system may include several cooling units such as for examplefreezer cases, freezer rooms, produce shelves, and refrigeration cases.Each unit uses the refrigerant to cool certain spaces to differenttemperatures.

In some instances, one or more of the units in a cooling system may leakrefrigerant into the retail space. For example, piping in the unit or ajoint in the piping may become loose and create a leak. In existingsystems, the entire cooling system may need to be shut down to diagnose,locate, and/or repair the leak. Additionally, the retail space may needto be evacuated to prevent customers and employees from being harmed bythe refrigerant leaking into the retail space. Thus, a simplerefrigerant leak may result in substantial loss of revenue for thestore.

This disclosure contemplates an unconventional cooling system thatdetects and responds to refrigerant leaks based on the detectedconcentrations of leaked refrigerant. The system includes a sensor thatdetects the concentration of leaked refrigerant in a space cooled by aload. When that detected concentration exceeds a first threshold, thesystem closes an expansion valve supplying refrigerant to the load tostop the flow of refrigerant to that load. If the leak continues and thedetected concentration exceeds a second threshold, the system activatesan exhaust system designed to evacuate the leaked refrigerant from thespace. In this manner, when a leak is first detected, the leak may beisolated from the rest of the cooling system, which may cause the leakto stop. The leaking unit may then be inspected and repaired withoutshutting down the rest of the cooling system. If the leak continuesafter the unit is isolated, the exhaust system may expel the leakedrefrigerant from the store. As a result, the store may not need to beevacuated even though there is a refrigerant leak. The cooling systemwill be described in more detail using FIGS. 1 through 3.

FIG. 1 illustrates portions of an example cooling system 100. As shownin FIG. 1, system 100 includes one or more high side heat exchangers105, one or more loads 110, one or more compressors 120, and one or morecontrollers 125. Although not illustrated in FIG. 1, system 100 mayinclude any suitable component of a cooling system, such as for exampleexpansion valves, flash tanks, oil separators, etc. In particularembodiments, system 100 isolates refrigerant leaks and if the leak doesnot stop, expels the refrigerant from system 100.

High side heat exchanger 105 may remove heat from a refrigerant. Whenheat is removed from the refrigerant, the refrigerant is cooled. Thisdisclosure contemplates high side heat exchanger 105 being operated as acondenser, a fluid cooler, and/or a gas cooler. When operating as acondenser, high side heat exchanger 105 cools the refrigerant such thatthe state of the refrigerant changes from a gas to a liquid. Whenoperating as a fluid cooler, high side heat exchanger 105 cools liquidrefrigerant and the refrigerant remains a liquid. When operating as agas cooler, high side heat exchanger 105 cools gaseous refrigerant andthe refrigerant remains a gas. In certain configurations, high side heatexchanger 105 is positioned such that heat removed from the refrigerantmay be discharged into the air. For example, high side heat exchanger105 may be positioned on a rooftop so that heat removed from therefrigerant may be discharged into the air. As another example, highside heat exchanger 105 may be positioned external to a building and/oron the side of a building.

System 100 includes one or more loads 110 that use the refrigerant tocool a space 115. System 100 may include multiple loads 110 that eachcool their own respective spaces 115. In a retail setting, loads 110 maybe any cooling unit within the store such as for example produceshelves, refrigeration cases, freezer cases, and/or freezer rooms. Eachof these units may cool a respective space 115 to a differenttemperature. For example, freezer cases and freezer rooms may cool aspace 115 below freezing temperatures (e.g., at or below 32 degreesFahrenheit). Refrigeration cases and produce shelves may cool a space115 to temperatures above freezing (e.g., above 32 degrees Fahrenheit).

In some instances, leaks may occur in a load 110 of system 100. Forexample, piping carrying the refrigerant or a joint in the piping maycome loose and spring a leak. When the leak occurs, refrigerant may leakinto space 115 and out into the retail store. As described in moredetail in FIG. 2, system 100 can detect the leak and in response,isolate the load 110 and/or the space 115 where the leak is occurring.By isolating the leak, the leaking load 110 may be stopped to preventthe leak from continuing. If the leak continues then system 100 mayactivate an exhaust system in space 115 to expel leaked refrigerant fromspace 115 and from the retail store. As a result, system 100 may stoprefrigerant leaks without shutting down the entire system 100.Additionally, when leaks occur, they may be located, diagnosed, andrepaired without evacuating the store.

Refrigerant may flow from load 110 to compressors 120. This disclosurecontemplates system 100 including any number of compressors 120.Compressor 120 may compress the refrigerant and increase the pressure ofthe refrigerant. As a result, the heat in the refrigerant may becomeconcentrated and the refrigerant may become a high pressure gas, whichmay make it easier for high side heat exchanger 105 to remove heat fromthe refrigerant. Compressor 120 directs the compressed refrigerant tohigh side heat exchanger 105.

Controller 125 controls the operation of the various components ofsystem 100. For example, controller 125 can activate one or more of highside heat exchanger 105, load 110, and compressor 120. Controller 125may also deactivate these components. Controller 125 may activate and/ordeactivate any component of system 100. As shown in FIG. 1, controller125 includes a processor 130 and a memory 135. This disclosurecontemplates processor 130 and memory 135 being configured to performany of the functions of controller 125 described herein.

Processor 130 is any electronic circuitry, including, but not limited tomicroprocessors, application specific integrated circuits (ASIC),application specific instruction set processor (ASIP), and/or statemachines, that communicatively couples to memory 135 and controls theoperation of controller 125. Processor 130 may be 8-bit, 16-bit, 32-bit,64-bit or of any other suitable architecture. Processor 130 may includean arithmetic logic unit (ALU) for performing arithmetic and logicoperations, processor registers that supply operands to the ALU andstore the results of ALU operations, and a control unit that fetchesinstructions from memory and executes them by directing the coordinatedoperations of the ALU, registers and other components. Processor 130 mayinclude other hardware and software that operates to control and processinformation. Processor 130 executes software stored on memory to performany of the functions described herein. Processor 130 controls theoperation and administration of controller 125 by processing informationreceived from various components of system 100. Processor 130 may be aprogrammable logic device, a microcontroller, a microprocessor, anysuitable processing device, or any suitable combination of thepreceding. Processor 130 is not limited to a single processing deviceand may encompass multiple processing devices.

Memory 135 may store, either permanently or temporarily, data,operational software, or other information for processor 130. Memory 135may include any one or a combination of volatile or non-volatile localor remote devices suitable for storing information. For example, memory135 may include random access memory (RAM), read only memory (ROM),magnetic storage devices, optical storage devices, or any other suitableinformation storage device or a combination of these devices. Thesoftware represents any suitable set of instructions, logic, or codeembodied in a computer-readable storage medium. For example, thesoftware may be embodied in memory 135, a disk, a CD, or a flash drive.In particular embodiments, the software may include an applicationexecutable by processor 130 to perform one or more of the functions ofcontroller 125 described herein.

FIG. 2 illustrates portions of the cooling system 100 of FIG. 1. Asshown in FIG. 2, a load 110 is used to cool a space 115. Additionally,system 100 includes one or more expansion valves 205, one or moresensors 210, one or more exhaust systems 215, one or more casecontrollers 220, and one or more check valves 225. FIG. 2 illustratesthese components as being located within space 115. This disclosurecontemplates that these components may be located outside space 115. Inparticular embodiments, these components may operate to isolaterefrigerant leaks so that they may be located, diagnosed, and repairedwithout shutting down the entirety of system 100.

Expansion valve 205 is used to cool refrigerant entering load 110.Expansion valve 205 may receive refrigerant from any component of system100 such as for example high side heat exchanger 105 and/or a flashtank. Expansion valve 205 reduces the pressure and therefore thetemperature of the refrigerant. Expansion valve 205 reduces pressurefrom the refrigerant flowing into the expansion valve 205. Thetemperature of the refrigerant may then drop as pressure is reduced. Asa result, refrigerant entering expansion valve 205 may be cooler whenleaving expansion valve 205. The refrigerant leaving expansion valve 205is fed to load 110.

When a refrigerant leak is detected, expansion valve 205 may be closedto stop refrigerant from flowing to load 110. As a result, load 110 mayshut down. Load 110 and the leak are then effectively isolated from therest of system 100. The leak may then be located, diagnosed, andrepaired by locating load 110 and inspecting the piping around load 110for leaks. Any leaks may then be patched and/or repaired beforeactivating load 110 and opening expansion valve 205.

Sensor 210 may detect concentrations of refrigerant in system 100 suchas for example in space 115. Sensor 210 may report any detectedconcentrations of refrigerant to controller 125. When sensor 210 reportsa concentration of refrigerant in space 115 that exceeds a firstthreshold, controller 125 may determine that a refrigerant leak isoccurring. In response, controller 125 may instruct case controller 220to close expansion valve 205. As a result, case controller 220 may closeexpansion valve 205 and shut down load 110, thereby effectivelyisolating and stopping the refrigerant leak. If the refrigerant leakcontinues, sensor 210 may detect a concentration of refrigerant thatexceeds a second threshold. The second threshold is higher than thefirst threshold. In response, controller 125 may activate exhaust system215. This disclosure contemplates sensor 210 being configured to detectany concentration of refrigerant in space 115. Additionally, thisdisclosure contemplates the first and second thresholds being any value.Furthermore, this disclosure contemplates controller 125 performing anyaction in response to any number of thresholds of detectedconcentrations of refrigerants. In particular embodiments, the firstthreshold is 1,000 parts per million and the second threshold is 5,000parts per million.

Exhaust system 215 may include any number of vents, fans, exhausttubing, and any other appropriate components. Exhaust system 215 mayoperate these components (e.g., activating fans) to expel leakedrefrigerant from space 115 and cooling system 100. In certainembodiments, when sensor 210 detects a particular concentration ofrefrigerant in space 115, controller 125 may determine that the detectedconcentration is above a second threshold. In response, controller 125may activate exhaust system 215 to expel refrigerant from space 115. Inresponse, exhaust system 215 may activate (e.g., activating a fan) toexpel refrigerant from space 115. As a result, exhaust system 215 mayremove refrigerant from space 115 and keep a retail space safe. The leakmay then be located, diagnosed, and/or repaired without needing toevacuate the retail space.

Case controller 220 may control the operation of various components ofsystem 100. For example, case controller 220 may activate and/ordeactivate expansion valve 205 and/or load 110. When sensor 210 detectsa particular concentration of refrigerant in space 115, controller 125may determine that the detected concentration exceeds a first threshold.In response, controller 125 may instruct case controller 220 to closeexpansion valve 205 and/or to deactivate load 110. In response, casecontroller 220 may close expansion valve 205 and/or deactivate load 110to isolate and potentially stop the leak. When the leak has beenrepaired, case controller 220 may instruct expansion valve 205 to openand load 110 to activate. This disclosure contemplates case controller220 being located in space 115. In some embodiments, case controller 220may form a part of controller 125. This disclosure also contemplatescase controller 220 being located with controller 125 and/or being asubcomponent of controller 125. This disclosure also contemplates casecontroller 220 being a distributed controller along with controller 125.Case controller 220 may operate independently and separately fromcontroller 125 or case controller 220 may operate in conjunction withcontroller 125. As shown in FIG. 2, case controller 220 includes aprocessor 230 and memory 235. This disclosure contemplates processor 230and memory 235 being configured to perform any of the functions of casecontroller 220.

Processor 230 is any electronic circuitry, including, but not limited tomicroprocessors, application specific integrated circuits (ASIC),application specific instruction set processor (ASIP), and/or statemachines, that communicatively couples to memory 235 and controls theoperation of case controller 220. Processor 230 may be 8-bit, 16-bit,32-bit, 64-bit or of any other suitable architecture. Processor 230 mayinclude an arithmetic logic unit (ALU) for performing arithmetic andlogic operations, processor registers that supply operands to the ALUand store the results of ALU operations, and a control unit that fetchesinstructions from memory and executes them by directing the coordinatedoperations of the ALU, registers and other components. Processor 230 mayinclude other hardware and software that operates to control and processinformation. Processor 230 executes software stored on memory 235 toperform any of the functions described herein. Processor 230 controlsthe operation and administration of case controller 220 by processinginformation received from various components of system 100. Processor230 may be a programmable logic device, a microcontroller, amicroprocessor, any suitable processing device, or any suitablecombination of the preceding. Processor 230 is not limited to a singleprocessing device and may encompass multiple processing devices.

Memory 235 may store, either permanently or temporarily, data,operational software, or other information for processor 230. Memory 235may include any one or a combination of volatile or non-volatile localor remote devices suitable for storing information. For example, memory235 may include random access memory (RAM), read only memory (ROM),magnetic storage devices, optical storage devices, or any other suitableinformation storage device or a combination of these devices. Thesoftware represents any suitable set of instructions, logic, or codeembodied in a computer-readable storage medium. For example, thesoftware may be embodied in memory 235, a disk, a CD, or a flash drive.In particular embodiments, the software may include an applicationexecutable by processor 230 to perform one or more of the functions ofcase controller 220 described herein.

Check valve 225 prevents refrigerant from flowing back into load 110when expansion valve 205 is closed and when load 110 is deactivated.When load 110 is deactivated and expansion valve 205 is closed, a dropin pressure may occur in load 110, which effectively creates a suctionat the discharge of load 110. If check valve 225 is not present, thenrefrigerant from other components of system 100 may be sucked into load110 through the discharge of load 110. Check valve 225 preventsrefrigerant from backflowing through the discharge of load 110, whichprotects load 110 from damage. In particular embodiments, instead ofusing a check valve 225, a full port solenoid valve may be used instead.

In some embodiments, when sensor 210 detects a particular concentrationof refrigerant, controller 125 may determine that the detectedconcentration exceeds a particular threshold such as for example asecond threshold. In response controller 125 may activate an alarm toalert individuals in the retail space that a refrigerant leak isoccurring. The alarm may produce a visible and/or audible signal thatalerts others of the refrigerant leak. In some embodiments, the visualand audible signals may also alert others of the location of the leaksuch as for example in space 115.

In particular embodiments, system 100 includes a pressure transducerthat converts a pressure of the refrigerant to an electric signal. Forexample, the pressure transducer may be located near load 110 and it mayrespond to a pressure of the refrigerant at load 110. The pressuretransducer may convert a pressure of the refrigerant at load 110 into anelectric signal and communicate that signal to controller 125.Controller 125 may determine that a refrigerant leak is occurring inload 110 based on the electric signal. For example, when a refrigerantleak is occurring, the electric signal communicated by the pressuretransducer will indicate that the pressure of the refrigerant at load110 is decreasing. Controller 125 may determine based on that electricsignal that a leak is occurring and instruct case controller 220 toclose expansion valve 205, deactivate load 110, and/or activate exhaustsystem 215.

FIG. 3 is a flowchart illustrating a method 300 for operating thecooling system 100 of FIG. 1. In particular embodiments, variouscomponents of system 100 perform the steps of method 300. By performingmethod 300 refrigerant leaks may be isolated, located, and repairedwithout shutting down the entire system 100 and without evacuating aretail space served by cooling system 100.

A high side heat exchanger may begin by cooling a refrigerant in step305. In step 310, a load uses the refrigerant to cool a space. A sensordetects a concentration of the refrigerant in the space in step 315. Instep 320, a controller determines whether the detected concentration isabove a first threshold. If the detected concentration is not above thefirst threshold, method 300 concludes. If the detected concentration isabove the first threshold, then the controller may close an expansionvalve in step 325. For example, the controller may instruct a casecontroller to close the expansion valve. In step 330, the controllerthen determines whether a detected concentration is above a secondthreshold. If the detected concentration is not above the secondthreshold, method 300 concludes. If the detected concentration is abovethe second threshold, then the controller activates an exhaust system instep 335. By activating the exhaust system, the leaked refrigerant maybe expelled from the space.

Modifications, additions, or omissions may be made to method 300depicted in FIG. 3. Method 300 may include more, fewer, or other steps.For example, steps may be performed in parallel or in any suitableorder. While discussed as system 100 (or components thereof) performingthe steps, any suitable component of system 100 may perform one or moresteps of the method.

Modifications, additions, or omissions may be made to the systems andapparatuses described herein without departing from the scope of thedisclosure. The components of the systems and apparatuses may beintegrated or separated. Moreover, the operations of the systems andapparatuses may be performed by more, fewer, or other components.Additionally, operations of the systems and apparatuses may be performedusing any suitable logic comprising software, hardware, and/or otherlogic. As used in this document, “each” refers to each member of a setor each member of a subset of a set.

Although the present disclosure includes several embodiments, a myriadof changes, variations, alterations, transformations, and modificationsmay be suggested to one skilled in the art, and it is intended that thepresent disclosure encompass such changes, variations, alterations,transformations, and modifications as fall within the scope of theappended claims.

What is claimed is:
 1. An apparatus comprising: an expansion valveconfigured to cool a refrigerant; a load configured to use therefrigerant to cool a space; a sensor configured to detect aconcentration of the refrigerant in the space; an exhaust systemconfigured to evacuate the refrigerant from the space; and a controllerconfigured to: determine whether the detected concentration of therefrigerant in the space exceeds a first threshold; in response to adetermination that the detected concentration of the refrigerant exceedsthe first threshold, close the expansion valve; determine whether thedetected concentration of the refrigerant in the space exceeds a secondthreshold; and in response to a determination that the detectedconcentration of the refrigerant exceeds the second threshold, activatethe exhaust system.
 2. The apparatus of claim 1, wherein the controlleris further configured to activate an alarm in response to thedetermination that the detected concentration of the refrigerant exceedsthe second threshold.
 3. The apparatus of claim 1, further comprising acheck valve coupled to a discharge of the load and configured to preventthe refrigerant from backflowing into the load.
 4. The apparatus ofclaim 1, further comprising a full-port solenoid valve coupled to adischarge of the load and configured to prevent the refrigerant frombackflowing into the load.
 5. The apparatus of claim 1, wherein thefirst threshold is 1000 parts per million and the second threshold is5000 parts per million.
 6. The apparatus of claim 1, further comprisinga pressure transducer configured to convert a pressure of therefrigerant at the load to an electric signal, the controller furtherconfigured to determine that a refrigerant leak is occurring in the loadbased on the electric signal.
 7. The apparatus of claim 6, wherein theelectric signal indicates that the pressure of the refrigerant that theload is decreasing.
 8. A method comprising: cooling a refrigerant usingan expansion valve; using the refrigerant to cool a space proximate aload; detecting a concentration of the refrigerant in the space using asensor; determining whether the detected concentration of therefrigerant in the space exceeds a first threshold; in response to adetermination that the detected concentration of the refrigerant exceedsthe first threshold, closing the expansion valve; determining whetherthe detected concentration of the refrigerant in the space exceeds asecond threshold; and in response to a determination that the detectedconcentration of the refrigerant exceeds the second threshold,activating an exhaust system to evacuate the refrigerant from the space.9. The method of claim 8, further comprising activating an alarm inresponse to the determination that the detected concentration of therefrigerant exceeds the second threshold.
 10. The method of claim 8,further comprising preventing the refrigerant from backflowing into theload using a check valve coupled to a discharge of the load.
 11. Themethod of claim 8, further comprising preventing the refrigerant frombackflowing into the load using a full-port solenoid valve coupled to adischarge of the load.
 12. The method of claim 8, wherein the firstthreshold is 1000 parts per million and the second threshold is 5000parts per million.
 13. The method of claim 8, further comprising:converting, by a pressure transducer, a pressure of the refrigerant atthe load to an electric signal; and determining that a refrigerant leakis occurring in the load based on the electric signal.
 14. The method ofclaim 13, wherein the electric signal indicates that the pressure of therefrigerant that the load is decreasing.
 15. A system comprising: a highside heat exchanger configured to remove heat from a refrigerant; anexpansion valve configured to cool the refrigerant from the high sideheat exchanger; a load configured to use the refrigerant to cool aspace; a sensor configured to detect a concentration of the refrigerantin the space; an exhaust system configured to evacuate the refrigerantfrom the space; and a controller configured to: determine whether thedetected concentration of the refrigerant in the space exceeds a firstthreshold; in response to a determination that the detectedconcentration of the refrigerant exceeds the first threshold, close theexpansion valve; determine whether the detected concentration of therefrigerant in the space exceeds a second threshold; and in response toa determination that the detected concentration of the refrigerantexceeds the second threshold, activate the exhaust system.
 16. Thesystem of claim 15, wherein the controller is further configured toactivate an alarm in response to the determination that the detectedconcentration of the refrigerant exceeds the second threshold.
 17. Thesystem of claim 15, further comprising a check valve coupled to adischarge of the load and configured to prevent the refrigerant frombackflowing into the load.
 18. The system of claim 15, furthercomprising a full-port solenoid valve coupled to a discharge of the loadand configured to prevent the refrigerant from backflowing into theload.
 19. The system of claim 15, wherein the first threshold is 1000parts per million and the second threshold is 5000 parts per million.20. The system of claim 15, further comprising a pressure transducerconfigured to convert a pressure of the refrigerant at the load to anelectric signal, the controller further configured to determine that arefrigerant leak is occurring in the load based on the electric signal.21. The system of claim 20, wherein the electric signal indicates thatthe pressure of the refrigerant that the load is decreasing.